A conventional electrical switch will be described with reference to FIG. 10 disclosed in Japanese Patent Laid-Open No. 177980/1984. In FIG. 10, the electrical switch 1 is configured as follows. That is, a buckling beam 4 is attached to an end of a piezoelectric element 3 attached into a housing 2 so that the axis of the buckling beam 4 coincides with the direction of expansion/contraction of the piezoelectric element 3. An opposite end of the buckling beam 4 is supported by a concave portion 2u of the housing 2. A screw 7 is provided in the housing 2 so that the initial displacement of the buckling beam 4 can be adjusted and so that the screw 7 can function as a backstop.
The buckling beam 4 is provided with an arm 9 extended from a support portion of the buckling beam 4 at one end. A movable contact 9a is provided at a forward end of the arm 9. Stationary contacts 10a and 10b of a stationary contactor 10 are provided opposite to the movable contact 9a. 
The operation of the electrical switch configured as described above will be described with reference to FIG. 10. When a voltage is now applied to the piezoelectric element 3, axial displacement occurs in the buckling beam 4 as represented by the arrow A. The buckling beam 4 is deformed in a direction perpendicular to the displacement given to an end of the buckling beam 4, so that maximum displacement occurs in the center portion of the buckling beam 4. The opposite end of the buckling beam 4 rotates. In parallel with this rotation, the arm 9 also rotates, so that the displacement is enlarged at the forward end to thereby make the movable contact 9a touch the stationary contact 10a. 
Another conventional electrical switch will be described with reference to FIG. 11 disclosed in Japanese Patent Laid-Open No. 133527/1986. In FIG. 11, the electrical switch is configured as follows. That is, a piezoelectric element 13 having terminals 13a is provided in a housing 11 so that the piezoelectric element 13 is erected. A lever 15 is supported to a rack portion 14 of the housing 11 so that the lever 15 can rotate around a protrusive portion 15a of the lever 15 as a fulcrum. A protrusive portion 15b of the lever 15 is engaged with a free end of the piezoelectric element 13. A forward end 15c of the lever 15 abuts on a base portion of a movable contact piece 17.
Switching means 20 has a movable spring 18 which is separated from the movable contact piece 17 by cutting. The switching means 20 is formed so that it can make snap action operation. The movable contact piece 17 is locked onto a support piece 16 fixed to a base portion 12 of the housing 11 at its lower end. The movable contact piece 17 has a movable contact 17a at its upper end. Stationary contactors 22 and 23 are provided in an upper portion of the housing 11 so that the stationary contactors 22 and 23 are erected. Stationary contacts 22a and 23a are provided in lower portions of the stationary contactors 22 and 23 respectively.
The operation of the electrical switch configured as described above will be described with reference to FIG. 11. In a state in which no voltage is applied between the terminals 13a, the movable contact piece 17 is urged to rotate counterclockwise by the spring force of the movable spring 18 as shown in FIG. 11.
When a voltage is now applied between the terminals 13a, the voltage is applied to the piezoelectric element 13. As a result, the piezoelectric element 13 is expanded in the direction of the arrow Q to press the protrusive portion 15b of the lever 15, so that the lever 15 rotates counterclockwise around the protrusive portion 15a as a fulcrum. Hence, the forward end 15c of the lever 15 moves in the direction of the arrow R to thereby urge the movable contact piece 17 to move in the same direction. When the movable contact piece 17 moves by a predetermined distance, the movable contact piece 17 is inverted by the snap action operation so that the movable contact 17a touches the stationary contact 23a. 
On the other hand, when the voltage between the terminals 13a is cut off, the piezoelectric element 13 is contracted. As a result, the movable contact piece 17 rotates counterclockwise so that the movable contact 17a touches the stationary contact 22a. 
In the electrical switch 1 shown in FIG. 10, however, abrasion occurs in the concave portion 2u because the forward end portion of the buckling beam 4 is frictionally slid on the concave portion 2u of the housing 2 by the expansion of the piezoelectric element 3 in the direction of the arrow A. Hence, because the quantity of displacement of the forward end of the arm 9 varies largely in accordance with the abrasion, it is difficult to keep the contact pressure between the stationary contact 10a or 10b and the movable contact 9a at a proper value. There has been a problem that chattering occurs easily in contact between the stationary contact 10a or 10b and the movable contact 9a. 
There has been also a problem that the spring 7 is required for contracting the buckling beam 4 to bend the buckling beam 4 to thereby always rotate the arm 9 counterclockwise.
On the other hand, the electrical switch shown in FIG. 11 is complex in mechanism because the electrical switch has a displacement enlarging mechanism constituted by a lever 15 having protrusive fulcra 15a and 15b, and a snap action mechanism constituted by switching means 20. Moreover, because the operation of the snap action mechanism is impulsive, chattering occurs in contact between the stationary contact 22a or 23a and the movable contact 17a. There has been a problem that abrasion occurs easily due to the protrusive fulcra 15a and 15b as well as electrical abrasion in the contacts is intensive.